The field of the invention is feeder/crushers for use in underground coal mines and the like. It is concerned particularly with such a machine in which crushing forces are applied to material between a pair of vertical breaker drums and not to the conveyor chain. The invention is also concerned with such a machine in which the crushed product size can be changed by adjusting the horizontal space between the breaker drums. The capability of adjusting the size of the crushed product without moving the breaker drum vertically is a special advantage for machines designed to operate in low-clearance coal mines.
In coal mines, the coal often comes off the face in a wide variety of sizes, some too large to be carried on the conveying system. To reduce such coal to a manageable size consist, feeder/crusher machines are employed to receive as-mined coal from a mining or loading machine or a haulage vehicle, crush the large lumps to a manageable size, and feed it to a main line conveyor for movement out of the mine.
Conventional feeder/crushers are self-propelled machines with a double strand chain flight conveyor continuously moving along the floor of the body to move as-mined coal from a receiving section to a rotary crusher and then move the crushed product to a discharge section from which it is loaded over the end or side of a conveyor which may be one of a series of conveyors leading to the mine portal. Typically, in conventional room and pillar mining, the feeder/crusher machine may be located to discharge onto one of the stationary conveyors located nearest the face being mined. One or more haulage vehicles such as shuttle cars, ram cars or scoops will carry the freshly mined coal to the feeder/crusher machine.
Typical feeder/crusher machines are shown in Long U.S. Pat. No. 3,016,204 and Clonch U.S. Pat. No. 4,073,445. Actual commercial feeder/crusher machines being marketed in the United States are shown in the April, 1976 issue of "Coal Age" as follows: Page 15, Long-Airdox Company; Page 173, Owens Manufacturing, Inc.; Page 231, The W. R. Stamler Corporation; and Page 269, S & S Corporation. A feeder/crusher marketed by Continental Conveyor & Equipment Company, Inc. is illustrated on pages 160 and 263 of the September, 1978 "Coal Age".
All these conventional feeder/crusher machines are of the same general construction. They all have a horizontal breaker drum or rotary crusher mounted at a fixed or variable distance above the floor of a chain flight conveyor running along the floor of a conveyor trough. Typically, the breaker drum is of the hammer mill or impact type in which a horizontal rotating shaft is provided along its length with a plurality of radial striker arms or hammers. The shaft is disposed transversely of the body of the machine, and as the coal is moved into the striker arm or hammer circle between the shaft and floor of the conveyor trough, by the conveyor flights, it is struck and crushed. Unfortunately, in these conventional machines, the crushing forces are also directed downward against the conveyor flights and chains and replacement and repair of these parts create the need for costly and time consuming maintenance and down time.
No two coal seams are alike. Some are fairly homogenius with uniform fracture planes and are readily cut or shot off the face in maximum lump sizes which can be easily handled by the mine conveyor system. Other coals are rashy, being interspersed or interbedded with shales and clays, causing them to come off the face in slabs and blocks which have to be broken down before they can be carried on a conveyor. Still further, there are often substantial changes from one location to another in the same seam.
Coal seams also vary widely in methane content, trapped in the form of gas within the coal structure from primordiol times. In such mines, some care has to be taken in crushing the coal to avoid releasing so much methane that as it raises the proportion in the air to an explosive level. Where a mine is so "hot" with methane being released from the mined coal, it is desirable not to aggravate safety of the atmosphere by breaking up any more coal chunks or slabs than is absolutely necessary. For example, in an area near Grundy, W. Va., there is a commercially mined coal seam which is so "hot" with methane that a continuous miner can sump in only 18 inches before it has to back up and move over to let the methane clear out of the mine air stream. This particular seam also has irregular concentrations of rashy coal which comes down in large blocks and slabs. Here is a prime example of need for a feeder/crusher which is adjustable between a non-operating load in which it merely passes the mined material through without crushing, and a crushing mode in which the mined coal is crushed just sufficiently to carry it on the conveyor without crushing it to the point where excessive amounts of methane are released.
Thus, conventional feeder/crusher machines have certain drawbacks when used in underground coal mines. The rotary crusher is horizontal and directs the crushing forces to the conveyor flights and chains causing breakage. And the rotary crusher is positioned at a fixed spacing from the conveyor, incapable of being adjusted to vary the maximum sizes of crushed product. Further, inasmuch as the rotary crusher is horizontal, there are low-clearance head room conditions in many mines which make it impossible to lift the rotary crusher to an inoperative position without interfering with the mine roof.